Protecting device for electric detonators



Nov 9,1926. 150mm H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DETONATORSFiled NOV. 20. 1925 nvamkoz flarry Z Grarzi,

Patented Nov... 9, 1926.

UNITED STATES PATENT OFFICE.

HARRY I. GRANT, OF TAMAQUA, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDERCOMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

PROTECTING DEVICE FOR ELECTRIC DETONATORS.

Application filed November 20, 1925. Serial No, 70,365.

This invention relates to a protecting de-,

vice for electric detonators of. the character of that shown in mycopending application, SeriaLNo. 748,214, filed on November 6, 1924. I lLike the device of the application referred to, the protecting device ofthe present invention is intended to be applied to the lead-in wires ofelectric detonators and to serve, while in position, to establish ashort circuit between thetwo lead-in wires,

so that any stray currents imposed upon the lead-in wires,-outwardly ofthe point of application of said device, may not find their way to thedetonator and prematurely explode the same and so that no difference inpotential can be created between the said wires, inwardly of the pointof application of the device under the influence of accidental or straycurrents imposed upon said wires.

I am aware'of the fact that it has been proposed to short circuit themain firing cable leading from the blasting machine. However, thatmethod is of utility only at the time of use. An important object of thepresent inventionris to provide a structure which will be operative withrespect to the individual detonators, at all times between the time ofmanufacture of the detonator and until the same is actually exploded onthe job, the structure being of particular utility during the time thatthe detonator is being transported and while it.

is being handled about the work preliminary to the actual connection ofits lead wires to the main firing cable.

The present application is directed to the protection of a specific formof short circuiting shunt and method of applying the same to the lead-inwires of the individual blasting caps, with its inner end abutting andresting firmly against the terminal end the usual insulation of thedetonators. the provision of a structure of this character, which isused only once and then thrown away, it is of importance that it be of asimple and inexpensive nature and one adapted to be applied rapidly byautomatic 1nachinery-.- With this end in view, I have devised the shuntshown in the accompany' ing drawing wherein:

Fig. 1 is a side elevation of a detonator having the shunt appliedthereto,

Fig. 2 is a transverse sectional view of In.

through the shunt after the insertion of the Wises but beforecompression of the shunt an Fig. 3 is a view like Fig. 2 aftercompression of the shunt.

Like numerals designate corresponding parts in all of the figures of thedrawing.

Referring to the drawing, 5 designates the conventional electricdetonator and 6 and 7 designate the usual lead-in wires of saiddetonator.

In the ordinary use of the detonator the flow of current of sulficientstrength pastan igniting element 8, which connects the inner ends of thewires 6 and 7, explodes the detonator. The lead-in wires are insulated,as indicated at 9 and 10, for some distance from the detonator and theends of the leadin wires are left bare beyond the point where theinsulation terminates, to adaptthem for ready application to the firingcable, leading from a blasting machine.

The short circuiting shunt of the present invention comprises a block11, of lead, copper, aluminum or any other suitable conductive material.This block is grooved along its opposite edges as indicated at 12, 12for the reception of the wires 6 and 7. The grooves may be made of suchsize with respect to the diameter of the wires, that the wires willfrictionally wedge or bind therein, after having been once forced intosaid grooves. I prefer, though, to compress the material of the block,firmly into engagement with the wires, after the insertion of the latterin the grooves, so that accidental dislodgement of the shunt duringshipment or handling will be impossible.

When the time of use of the detonator arrives, the shunt may be removedbyv stripping it longitudinally from the lead wires 6 and 7 Thisstripping action not only removes the shunt but cleans and brightens the1 exposed ends of the wires so that they will make a good electricalconnection with the main firing cable of a blasting machine.

It is apparent that as long as the shunt is in place, a short circuit iscreated between wires 6 and 7 at its point of application, so thatdiflerences in electrical potential be- .tween said wires will not beeffective to explode the detonator. Since the shunt abuts the insulation9 and 10, it follows that the detonator is completely protected at allpoints. It is not to be understood that the device is of utility onlywhen actually touching the termination of the insulation. It will give avery appreciable measure of protection even when spaced somewhat fromthe insulation because the influences which might bring about suchdifference in potential between the lead wires as to explode thedetonator, are not those sought to be created by an intelligent humanagency but only those which might accidentally occur.

, Stray currents of such low E. M. F. as to escapeordinary noticeconstitute a marked source of danger and are rendered absolutelyharmless by this invention.

It is to be understood that the invention is not limited to the preciseconstruction set forth but that it includes within its purview Whateverchanges fairly come within either the terms or the spirit of theappended claims.

Having described my invention, what I claim is:

The combination with an individual electric detonator and its bifilarlead wires, said lead wires having their inner portions cov- Intestlmony whereof he afiixes his sig- 7 nature.

HARRY L. GRANT.

